Application of Boundary Conduction Mode Control in Galvanically Isolated Buck-Boost Converter

Focus is on the boundary conduction mode (BCM) operation of the quasi-Z-source isolated buck-boost converter (qZS-IBBC). BCM control is applied to the buck and boost modes independently and by different methods. The operating principle and control of the converter in both modes are analyzed. BCM control for the performance improvement of the converter is evaluated by theoretical analysis. It was found that the efficiency and performance of the converter can be improved in both modes. In the buck mode, BCM control improves the efficiency by reducing conduction losses; in the boost mode, the performance is enhanced by improving switching losses. Finally, a 300 W prototype is tested to validate the concept for effectiveness and correctness.